Aqueous metal surface treatment agent for lithium ion secondary battery

ABSTRACT

This is to provide an aqueous metal surface treatment agent for a lithium ion secondary battery which can improve interlaminar adhesiveness between a metal member and a resin coating layer such as a film or a coated film, and solvent resistance without using trivalent chromium. 
     The aqueous metal surface treatment agent for a lithium ion secondary battery comprises a polyvinyl alcohol resin containing 2 to 15 mol % of a 1,2-diol structural unit represented by the formula (1): 
     
       
         
         
             
             
         
       
     
     having a degree of saponification of 90 to 99.9 mol % and an average degree of polymerization of 250 to 3000; and a metallic crosslinking agent.

TECHNICAL FIELD

The present invention relates to an aqueous metal surface treatmentagent for a lithium ion secondary battery comprising a modifiedpolyvinyl alcohol having a 1,2-diol structural unit and a metalliccrosslinking agent.

BACKGROUND ART

A treatment agent for treating the surface of a metal has been used inbroad fields such as automobiles, home electric appliances,architecture, foods, medicines, etc., in particular, it is useful forimproving interlaminar adhesiveness between a metal material such asaluminum, magnesium, copper, iron, zinc, nickel or an alloy thereof, andvarious resin coating layers provided on the surface thereof, solventresistance of the resin coating layer and corrosion resistance of themetal material.

Examples of the metal surface treatment agent of the prior art includean aqueous treating solution using trivalent chromium (Patent Literature1). This treating agent can be used without using hexavalent chromiumhaving high toxicity, but when it is exposed to high temperatureenvironment, oxidation of chromium proceeds to generate hexavalentchromium. Thus, there are problems of environment.

In view of such a background, non-chromium treating agents have beeninvestigated variously until now. In particular, in the uses whichrequire corrosion resistance, adhesiveness with a paint, a resin or thelike, there are problems that the performances are insufficient.Therefore, trivalent chromium treating agents which are harmful to humanbody or environment have yet been used.

Among these, a package for a lithium secondary battery, a film-attachedtab lead member and the like are required to have severe adhesionreliability such as electrolyte resistance, HF resistance and the like,in the adhesion of a polyolefin film such as polyethylene andpolypropylene with a metal such as aluminum, copper and nickel, andvarious non-chromium type techniques have been published (PatentLiterature 2). However, it is the present status that the non-chromiumtype treating agents are inferior in surface treatment performances tothose of the conventional trivalent chromium type treating agent.

PRIOR ART LITERATURES Patent Literatures

[Patent Literature 1] JP 2006-40595A

[Patent Literature 2] JP 2006-202577A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide an aqueous metalsurface treatment agent for improving interlaminar adhesiveness betweena metal member for a lithium ion secondary battery and a resin coatinglayer such as a film or a coated film, and solvent resistance, withoutusing chromium.

Means to Solve the Problems

The present invention relates to

(1) an aqueous metal surface treatment agent for a lithium ion secondarybattery which comprises a polyvinyl alcohol resin containing 2 to 15 mol% of a 1,2-diol structural unit represented by the following formula(1):

wherein R¹, R² and R³ each independently represent a hydrogen atom or anorganic group, X represents a single bond or a bonding chain, and R⁴,R⁵, and R⁶ each independently represent a hydrogen atom or an organicgroup, and having a degree of saponification of 90 to 99.9 mol % and anaverage degree of polymerization of 250 to 3000; and a metalliccrosslinking agent;

(2) the above mentioned metal surface treatment agent for a lithium ionsecondary battery wherein a molar ratio of the polyvinyl alcohol resin:the metallic crosslinking agent is 1:5 to 500:1;

(3) the above mentioned metal surface treatment agent for a lithium ionsecondary battery wherein the metallic crosslinking agent is selectedfrom the group consisting of an oxide, a hydroxide, a complex compound,an organometallic compound, an organic acid salt and an inorganic acidsalt of titanium, aluminum, zirconia, vanadium, molybdenum, cerium,lanthanum or tungsten.

Effects of the Invention

The present invention can improve interlaminar adhesiveness between ametal member and a resin coating layer such as a film or a coated film,and solvent resistance, without using trivalent chromium.

DESCRIPTION OF EMBODIMENTS

The metal surface treatment agent of the present invention is an aqueouscomposition containing a specific polyvinyl alcohol resin (also referredto as PVA resin), and a metallic crosslinking agent.

(Polyvinyl alcohol resin)

The polyvinyl alcohol resin in the present invention contains 2 to 15mol % of a 1,2-diol structural unit represented by the formula (1):

wherein R¹, R² and R³ each independently represent a hydrogen atom or anorganic group, X represents a single bond or a connecting chain, and R⁴,R⁵ and R⁶ each independently represent a hydrogen atom or an organicgroup, and having a degree of saponification (measured according to JISK6726) of 90 to 99.9 mol % and an average degree of polymerization of250 to 3000.

R¹ to R³ and R⁴ to R⁶ in the 1,2-diol structural unit represented by theformula

(1) are desirably all hydrogen atoms, and a PVA resin having astructural unit represented by the formula (1′):

is suitably used.

R¹ to R³ and R⁴ to R⁶ in the structural unit represented by the formula(1) may be an organic group which does not markedly impair thecharacteristics of the resin. The organic group is not particularlylimited and preferably, for example, an alkyl group having 1 to 4 carbonatoms such as a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert- butylgroup and the like, and the organic group may have a substituent(s) suchas a halogen group, a hydroxy group, an ester group, a carboxylic acidgroup, a sulfonic acid group and the like, if necessary.

X in the 1,2-diol structural unit represented by the formula (1) is asingle bond or a connecting chain. In the points of thermal stabilityand structural stability under high temperature/acidic conditions, X ismost preferably a single bond, and may be a connecting chain in therange it does not inhibit the effects of the present invention. Such aconnecting chain is not particularly limited and may be mentioned, inaddition to a hydrocarbon (these hydrocarbons may be substituted by ahalogen such as fluorine, chlorine, bromine and the like) such asalkylene, alkenylene, alkynylene, phenylene, naphthylene and the like,—O—, —(CH₂O)_(m)—, —(OCH₂)_(m)—, —(CH₂O)_(m)CH₂—, —CO—, —COCO—,—CO(CH₂)_(m)CO—, —CO(C₆H₄)CO—, —S—, —CS—, —SO—, —SO₂—, —NR—, —CONR—,—NRCO—, —CSNR—, —NRCS—, —NRNR—, —HPO₄—, —Si(OR)₂—, —OSi(OR)₂—,—OSi(OR)₂O—, —Ti(OR)₂—, —OTi(OR)₂—, —OTi(OR)₂O—, —Al(OR)—, —OAl(OR)—,—OAl(OR)O—(Rs are each independently an optional substituent, preferablya hydrogen atom or an alkyl group, and m is a natural number andpreferably 1 or 2) and the like. Among these, in the points of stabilityat the time of preparation or at the time of use, the connecting chainis preferably an alkylene group having 6 or less carbon atoms,particularly preferably a methylene group or —CH₂OCH₂—.

A degree of saponification (measured according to JIS K6726) of the PVAresin used in the present invention is 90.0 to 99.9 mol %, preferably95.0 to 99.9 mol %, more preferably 97.0 to 99.9 mol %. If the degree ofsaponification is lower than 90.0 mol, the crosslinking density may belowered and a film strength or water resistance become to beinsufficient. Also, the PVA resin having higher than 99.9 mol % isdifficultly prepared so that it is not preferred. The degree ofsaponification in the present invention is defined to be a molar numberof the hydroxy group based on the total (mol) of the modified groupmoiety like derived from 3,4-diacyloxy-1-butene, and a vinyl ester suchas vinyl acetate and the like.

An average degree of polymerization measured according to JIS K6726 ofthe PVA resin of the present invention is 250 to 3000, particularly 300to 2800 or 400 to 2700, further 420 to 2500, 450 to 2000 or 1000 to 1500is preferably used.

A content of the 1,2-diol structural unit contained in the PVA resin is2 to 15 mol %, particularly 3 to 13 mol %, further 5 to 10 mol % ispreferred. The content of the 1,2-diol structural unit in the PVA resincan be obtained from ¹H-NMR spectrum (solvent: DMSO-d₆, internalstandard: tetramethylsilane) of the completely saponified

PVA resin. Specifically, it can be calculated from peak areas derivedfrom a hydroxy group proton, a methyne proton, a methylene proton, amethylene proton in the main chain, and a hydroxy group protonconnecting to the main chain and the like in the 1,2-diol unit.

The PVA resin which can be used in the present invention can be preparedby the method described in, for example, JP 2009-149865A or WO2009-069644A pamphlet.

(Metallic crosslinking agent)

The metallic crosslinking agent in the present invention is not limitedso long as it is a metal compound having an ability of crosslinking thePVA resin, but the metal does not include Cr. The metallic crosslinkingagent includes, for example, a metal compound containing one or moremetals selected from the group consisting of Ti, Zr, Al, V, Mo, Ce, Laand W. The metal compound is not particularly limited, and includes, forexample, an oxide, a hydroxide, a complex compound, an organometalliccompound, a metal alkoxide, an organic acid salt and an inorganic acidsalt of these metals and the like.

Specifically, the complex compound includes titaniumdiisopropoxybis(triethanolaminate), titanium lactate, titaniumtetrakisacetonate, ammonium bis(oxalato)oxotitanate, zirconiumtetrakis(acetylacetonato), zirconium tributoxy(monoacetylacetonate),zirconium acetylacetonate, tetrakis(dimethylamino) zirconium,aminocarboxylic acidic zirconium, aluminum tris(acetylacetonate),vanadyl acetylacetonate, vanadium acetylacetonate, molybdenum dioxideacetylacetonate, lanthanum acetylacetonate, cerium acetylacetonate,ammonium pentanitratocerate, ammonium hexanitratocerate, tungstenacetylacetonate, hexacarbonyl tungsten and the like.

The organometallic compound includes tetraisopropyl titanate, tetrabutyltitanate, tetrapropyl zirconate, tetrabutyl zirconate, triisobutylaluminum, tungsten hexacarbonyl and the like.

The metal alkoxide includes titanium methoxide, titanium ethoxide,titanium propoxide, titanium butoxide, zirconium methoxide, zirconiumethoxide, zirconium butoxide, zirconium propoxide, aluminum ethoxide,aluminum butoxide, vanadium methoxide, vanadium ethoxide, vanadiumpropoxide, vanadium butoxide, vanadium aluminum propoxide, molybdenummethoxide, molybdenum ethoxide, molybdenum isopropoxide, molybdenumbutoxide, molybdenum phenoxide, molybdenum phenylethoxide, molybdenumphenoxyethoxide, cerium methoxide, cerium ethoxide, cerium isopropoxide,cerium butoxide, lanthanum methoxide, lanthanum ethoxide, lanthanumisopropoxide, lanthanum butoxide, tungsten methoxide, tungsten ethoxide,tungsten isopropoxide, tungsten butoxide and the like.

The organic acid salt includes titanium acetate, titanium citrate,titanium oxalate, ammonium oxydioxalate, titanium tetraoleate, zirconiumoctanoate, zirconium acetate, zirconyl acetate, zirconium octylate,zirconyl octylate, aluminum oxalate, aluminum tartrate, aluminumbenzoate, aluminum oleate, aluminum citrate, aluminum gluconate,aluminum stearate, aluminum lactate, aluminum butyrate, vanadiumacetate, vanadium oxyoxalate, vanadium octanoate, vanadium naphthenate,molybdenum acetate, molybdenum butyrate, lanthanum octanoate, lanthanumformate, lanthanum acetate, lanthanum oxalate, lanthanum stearate,cerium acetate, cerium oxalate, cerium stearate, and the like.

The inorganic acid salt includes titanium chloride, titaniumhydrofluoride, titanium nitrate, titanium oxynitrate, zirconiumchloride, fluorozirconic acid, zirconium chloride oxide, zirconiumphosphate, ammonium zirconium carbonate hydroxide, ammonium zirconiumcarbonate, zirconium silicate, zirconium nitrate, zirconium sulfate,zirconium titanate, aluminum chloride, aluminum phosphate, aluminumsulfate, aluminum nitrate, aluminum perchlorate, aluminum titanate,vanadium chloride, vanadium dichloride oxide, vanadium trichlorideoxide, ammonium metavanadate, vanadyl sulfate, vanadium titanate,molybdenum chloride, molybdenum sulfate, molybdenum nitrate, molybdenumphosphate, molybdic acid, ammonium molybdate, lanthanum chloride,lanthanum perchlorate, lanthanum dititanate, lanthanum sulfate,lanthanum phosphate, cerium chloride, cerium perchlorate, ceriumnitrate, cerium sulfate, cerium phosphate, tungsten chloride, tungstendichloride dioxide, tungsten carbonate, sodium tungstate, ammoniumtungstate, ammonium phosphotungstate and the like. Preferred metalliccrosslinking agent includes titanium diisopropoxybis(triethanolaminate),titanium lactate, aminocarboxylic acidic zirconium, zirconium nitrate,aluminum trisacetylacetonate, vanadyl acetylacetonate, vanadiumacetylacetonate, molybdenum dioxide acetylacetonate, lanthanumacetylacetonate, cerium acetylacetonate and tungsten acetylacetonate.

(Molar ratio of polyvinyl alcohol resin:metallic crosslinking agent)

In the present invention, a molar ratio of the polyvinyl alcohol resin:the metallic crosslinking agent is preferably 1:5 to 500:1, morepreferably 1:3 to 300:1, particularly preferably 1:2.5 to 100:1, andmost preferably 10:1 to 100:1. Here, calculation of the molar ratio tothe metallic crosslinking agent can be carried out based on anintroduced amount of the modified group such as a group derived from3,4-diacyloxy-1-butene of the polyvinyl alcohol resin and an averagemolecular weight of the monomer unit obtained depending on the degree ofsaponification.

(Amounts of polyvinyl alcohol resin and metallic crosslinking agent)

In the aqueous surface treatment agent of the present invention, a totalamount of the polyvinyl alcohol resin and the metallic crosslinkingagent based on the whole treatment agent is preferably 0.01 to 20% byweight, more preferably 0.1 to 10% by weight, particularly preferably0.5 to 5% by weight. The remainder of the treatment agent other than thepolyvinyl alcohol resin and the metallic crosslinking agent can be wateror an aqueous solvent, for example, a mixture of water and awater-soluble alcohol, and the like.).

(Optional component)

The surface treatment agent of the present invention may contain aconventionally used additive(s) within the range which does not impairthe effects of the present invention in addition to the polyvinylalcohol resin, the metallic crosslinking agent and water or an aqueoussolvent. The additive includes an organic compound having one or morecarboxyl group in the molecule (for example, an organic acid such asacetic acid, oxalic acid, malonic acid, malic acid, tartaric acid,mellitic acid and the like.), a rheology characteristic improver (athixotropic property improver), a pH adjustor, an antiseptic, anantioxidant and the like.

(Surface treatment method)

There is a surface treatment method of a metal member including the stepof treating the surface of a metal member using the metal surfacetreatment agent of the present invention.

The metal member is not particularly limited so long as it is a memberof a shapable metal and a metal member on the surface of which isprovided a resin coating layer, and includes for example, aluminum,magnesium, copper, iron, zinc, nickel, stainless, and an alloy thereof.The metal of the metal member is preferably aluminum, copper, nickel andstainless, particularly preferably aluminum, copper and nickel. Themetal member includes a metal case for electronic parts, a package for alithium secondary battery, a film-attached tab lead member and a tabterminal.

Surface treatment of a metal member can be carried out by theconventionally known methods such as roll coating, spin coating, dippingmethod, spraying method and the like. According to the treatment methodof the present invention, aging treatment can be carried out at 100 to200° C., preferably at 100 to 160° C., for 5 seconds to 60 minutes,preferably for 10 seconds to 30 minutes after the treatment such ascoating and the like. Improved effects in corrosion resistance andadhesiveness with a resin material can be obtained by the agingtreatment. A film of the metal surface treatment agent obtained by agingtreatment preferably has a thickness of 0.01 to 10 μm, particularlypreferably 0.1 to 3 μm.

There is metal member surface-treated by the treating agent of thepresent invention. A resin coating layer may be formed on the surface ofthe surface-treated metal member. Interlaminar adhesiveness between themetal member and the resin coating layer such as a film or a coatedfilm, and solvent resistance can be improved. The resin coating layerincludes a polymer film or a coating film having mechanical strength,sealability, electric insulation, heat resistance and/or solventresistance and the like. The polymer includes a polyolefin such aspolyethylene, polypropylene and the like, polyester, polyamide,polyimide, poly(vinylidene fluoride), urethane and the like, and ispreferably a polyolefin such as polyethylene, polypropylene and thelike.

There is metal component which contain a resin coating layer on thesurface of the metal member surface-treated by the treating agent of thepresent invention. The resin coating layer can be provided on thesurface of the surface-treated metal member according to theabove-mentioned conventionally known method. It can be prepared, forexample, by hot-melting a polymer film on the surface of thesurface-treated metal member, or a polymer is coated on the surface ofthe surface-treated metal member to form a coated film. The metalcomponent includes a metal member coated by a resin coating layer, forexample, a metal case for electronic parts, a metal laminate package fora lithium secondary battery and/or a capacitor, film-attached tab leadmember, a surface treated tab terminal, metal/resin mold parts and thelike.

There is article which contains the metal component treated by thetreating agent of the present invention. The article is not particularlylimited so long as it contains metal component including a metalmaterial such as aluminum, magnesium, copper, iron, zinc, nickel and analloy thereof, and various resin coating layers provided on the surfacethereof, and can be article of wide range of fields such as automobile,home electric appliances, architecture, foods, medicines and the like.The article may be preferably, for example, a laminate package typebattery, a laminate package type capacitor, an inside seal forautomobile, a glass channel and the like.

EXAMPLES

[Preparation of PVA resin (A1)]

In a reaction vessel equipped with a reflux condenser, a dropping funneland a stirrer were charged 1000 parts of vinyl acetate, 400 parts ofmethanol and 120 parts of 3,4-diacetoxy-1-butene, and then, 0.06 mol %(based on the charged vinyl acetate) of azobisisobutyronitrile was addedto the mixture. The temperature of the mixture was raised under nitrogenstream and stirring, and polymerization was started at boiling point. Atthe time when the degree of polymerization of vinyl acetate became 75%,m-dinitrobenzene was added to the mixture to stop the polymerization,subsequently the unreacted vinyl acetate monomer was removed outside bythe method of blowing a methanol vapor to prepare a methanol solution ofthe copolymer.

Then, the above-mentioned methanol solution was further diluted withmethanol to adjust the concentration to 30% and charged in a kneader.While maintaining the solution temperature to 35° C., 2% methanolsolution of sodium hydroxide was added in such an amount that it became8 mmol based on the total 1 mol of the vinyl acetate structural unit andthe 3,4-diacetoxy-1-butene structural unit in the copolymer to carry outsaponification. With the progress of the saponification, saponifiedproducts were precipitated and when they became particulate states, theywere collected by filtration, washed well with methanol and dried in ahot air drier to prepare an objective PVA resin (A1).

When the degree of saponification of the obtained PVA resin (A1) wasanalyzed by an amount of the residual vinyl acetate and a consumedamount of an alkali required for hydrolysis of 3,4-diacetoxy-1-butene,it was 99.4 mol %. Also, when the average degree of polymerization wasanalyzed according to JIS K 6726, it was 1200. Further, when the contentof the 1,2-diol structural unit represented by the formula (1′) wascalculated from the integrated value measured by ¹H-NMR (300 MHz protonNMR, d6-DMSO solution, internal standard substance; tetramethylsilane,50° C.), it was 5.7 mol %, and the average molecular weight of themonomer unit calculated therefrom was 46.8.

[Preparation of PVA resin (A2)]

In a reaction vessel equipped with a reflux condenser, a dropping funneland a stirrer were charged 1000 parts of vinyl acetate, 1120 parts ofmethanol and 65.3 parts of 3,4-diacetoxy-1-butene, then, 0.11 mol %(based on the charged vinyl acetate) of azobisisobutyronitrile was addedto the mixture. The temperature of the mixture was raised under nitrogenstream and stirring, and polymerization was started at boiling pointsimultaneously addition of 20% methanol solution of3,4-diacetoxy-1-butene was started according to the HANNA method, whichwas added in an amount of 93.58 parts until the degree of polymerizationbecame 95%.

Incidentally, 3,4-diacetoxy-1-butene was so charged that it reacts withvinyl acetate uniformly in an amount obtained from a HANNA equation[Reactivity ratio (r) of 3,4-diacetoxy-1-butene=0.701, Reactivity ratio(r) of vinyl acetate=0.710] so as to comply with the polymerizationrate. When the degree of polymerization of the vinyl acetate became 95%,10 ppm of m-dinitrobenzene (based on the charged vinyl acetate) wasadded to the mixture as a polymerization inhibitor to terminate thepolymerization. Subsequently, the unreacted vinyl acetate monomer wasremoved outside by the method of blowing a methanol vapor therein toobtain a methanol solution of the copolymer. Then, the above-mentionedmethanol solution was further diluted with methanol to adjust theconcentration to 30% and charged in a kneader. While maintaining thesolution temperature to 35° C., 2% methanol solution of sodium hydroxidewas added in such an amount that it becomes 9 mmol based on the total 1mol of the vinyl acetate structural unit and the 3,4-diacetoxy-1-butenestructural unit in the copolymer to carry out saponification. With theprogress of the saponification, saponified products were precipitatedand when they became particulate states, they were collected byfiltration, washed well with methanol and dried in a hot air drier toprepare an objective PVA resin (A2).

When the degree of saponification of the obtained PVA resin (A2) wasanalyzed by an amount of the residual vinyl acetate and a consumedamount of an alkali required for hydrolysis of 3,4-diacetoxy-1-butene,it was 99.5 mol %. Also, when the average degree of polymerization wasanalyzed according to JIS K 6726, it was 470. Further, when the contentof the 1,2-diol structural unit represented by the formula (1′) wascalculated from the integrated value measured by ¹H-NMR (300 MHz protonNMR, d6-DMSO solution, internal standard substance; tetramethylsilane,50° C.), it was 5.8 mol %, and the average molecular weight of themonomer unit calculated therefrom was 46.8.

[Preparation of PVA resin (A3)]

In a reaction vessel equipped with a reflux condenser, a dropping funneland a stirrer were charged 1000 parts of vinyl acetate, 450 parts ofmethanol and 60 parts of 3,4-diacetoxy-1-butene, then, 0.055 mol %(based on the charged vinyl acetate) of azobisisobutyronitrile was addedto the mixture. The temperature of the mixture was raised under nitrogenstream and stirring, and polymerization was started. At the time whenthe degree of polymerization of vinyl acetate became 80%,m-dinitrobenzene was added to the mixture to stop the polymerization,subsequently the unreacted vinyl acetate monomer was removed outside bythe method of blowing a methanol vapor to prepare a methanol solution ofthe copolymer.

Then, the above-mentioned methanol solution was further diluted withmethanol to adjust the concentration to 30% and charged in a kneader.While maintaining the solution temperature to 35° C., 2% methanolsolution of sodium hydroxide was added in such an amount that it became8 mmol based on the total 1 mol of the vinyl acetate structural unit andthe 3,4-diacetoxy-1-butene structural unit in the copolymer to carry outsaponification. With the progress of the saponification, saponifiedproducts were precipitated and when they became particulate states, theywere collected by filtration, washed well with methanol and dried in ahot air drier to prepare an objective PVA resin (A3).

When the degree of saponification of the obtained PVA resin (A3) wasanalyzed by an amount of the residual vinyl acetate and a consumedamount of an alkali required for hydrolysis of 3,4-diacetoxy-1-butene,it was 99.6 mol %. Also, when the average degree of polymerization wasanalyzed according to JIS K 6726, it was 1200. Further, when the contentof the 1,2-diol structural unit represented by the formula (1′) wascalculated from the integrated value measured by ¹H-NMR (300 MHz protonNMR, d6-DMSO solution, internal standard substance; tetramethylsilane,50° C.), it was 2.9 mol %, and the average molecular weight of themonomer unit calculated therefrom was 45.4.

In accordance with the preparation method of the above-mentioned PVAresins (A1) to (A3), the following PVA resins (A4) to (A7) shown inTable 1 were prepared.

TABLE 1 Degree of Average molecular Content of 1,2-diol saponificationweight of recurring Average degree of structural unit PVA resin (mol %)structural unit polymerization (mol %) A4 99.8 45.7 1800 3.8 A5 99.347.6 1300 7.4 A6 98.5 45.3 2700 1.48 A7 98.8 49.2 400 10.7

[1. Corrosion resistance of the surface treated aluminum foil, andadhesiveness thereof with PP film]

(1) Metal member

An aluminum foil of a 1085 material (both glossy) cut to a shape havinga thickness of 20 μm, a width of 1.5 cm, and a length of 4 cm was usedas a metal member.

(2) Alkali degreasing

The metal member was degreased by dipping it in a 10 wt % aqueous sodiumhydroxide solution for 10 seconds. After the degreasing treatment, themetal member was dipped in deionized water for 20 seconds twice to carryout the washing.

(3) Preparation of the treating agent of the present invention andsurface treatment (treatment using a modified PVA having a 1,2-diolstructural unit, and metallic crosslinking agent)

By using the above-mentioned PVA resins (A1 to A3), and startingmaterials shown in Table 2, as shown in the following mentioned Examples1-1 to 1-9, X-1, Y-1 and 1-10 to 1-18 and Comparative examples Z-1 andZ-2, treating agents of Examples of the present invention andComparative examples were prepared, and a surface treatment of the metalmembers were carried out by using these.

TABLE 2 Degree of Molecular Degree of saponifcation Name of materialweight polymerization (mol %) Others Unmodified PVA 2400 98.0~99.0TC-400 (available from 461.9 — — Titanium diisopropoxy- Matsumoto Finebis(triethanolaminate) Chemical Co., Ltd.) TC-310 (available from 259.9— — Titanium lactate Matsumoto Fine Chemical Co., Ltd.) Zircosol AC7(available 263.2 — — Ammonium zirconium from Daiichi Kigenso carbonateKagaku Kogyo Co., Ltd.)

Example 1-1

Into deionized water were dissolved PVA resin (A1) and TC-400 with amolar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.8 μm.

Example 1-2

Into deionized water were dissolved PVA resin (A1) and TC-400 with amolar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 160° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.7 μm.

Example 1-3

Into deionized water were dissolved PVA resin (A1) and TC-400 with amolar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 200° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.9 μm.

Example 1-4

Into deionized water were dissolved PVA resin (A1) and TC-400 with amolar ratio of 10:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.8 μm.

Example 1-5

Into deionized water were dissolved PVA resin (A1) and TC-400 with amolar ratio of 100:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.6

Example 1-6

Into deionized water were dissolved PVA resin (A1) and TC-400 with amolar ratio of 30:1 to obtain 5 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 3.1 μm.

Example 1-7

Into deionized water were dissolved PVA resin (A1) and TC-400 with amolar ratio of 30:1 to obtain 0.5 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.4 μm.

Example 1-8

Into deionized water were dissolved PVA resin (A1) and TC-310 with amolar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.7 μm.

Example 1-9

Into deionized water were dissolved PVA resin (A1) and Zircosol AC7 witha molar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.7 μm.

Example X-1

Into deionized water were dissolved PVA resin (A2) and TC-400 with amolar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.8 μm.

Example Y-1

Into deionized water were dissolved PVA resin (A3) and TC-400 with amolar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.8

Comparative Example Z-1

Into deionized water were dissolved unmodified PVA and TC-400 with amolar ratio of 30:1 to obtain 2 wt % of a treating agent. An aluminumfoil which had been subjected to alkali degreasing (2) was dipped in theobtained treating agent, then, aging thereof was carried out at 100° C.for 30 minutes to carry out a surface treatment. A thickness of thesurface treated film after aging was 2.9 μm.

Example 1-10

Into deionized water were dissolved PVA resin (A1), TC-400 (B 1) andfluorozirconic acid (B2) with a molar ratio of 30:1:25 to obtain 5 wt %of a treating agent. An aluminum foil which had been subjected to alkalidegreasing (2) was dipped in the obtained treating agent, then, agingthereof was carried out at 100° C. for 30 minutes to carry out a surfacetreatment. A thickness of the surface treated film after aging was 1.4μm.

Example 1-11

Into deionized water were dissolved PVA resin (A1), TC-400 (B1) andfluorozirconic acid (B2) with a molar ratio of 30:1:25 to obtain 5 wt %of a treating agent. An aluminum foil which had been subjected to alkalidegreasing (2) was dipped in the obtained treating agent, then, agingthereof was carried out at 160° C. for 1 minute to carry out a surfacetreatment. A thickness of the surface treated film after aging was 1.5μm.

Example 1-12

Into deionized water were dissolved PVA resin (A4), TC-400 (B1) andfluorozirconic acid (B2) with a molar ratio of 30:1:25 to obtain 5 wt %of a treating agent. An aluminum foil which had been subjected to alkalidegreasing (2) was dipped in the obtained treating agent, then, agingthereof was carried out at 160° C. for 1 minute to carry out a surfacetreatment. A thickness of the surface treated film after aging was 1.5μm.

Example 1-13

Into deionized water were dissolved PVA resin (A5), TC-400 (B1) andfluorozirconic acid (B2) with a molar ratio of 30:1:13 to obtain 2.7 wt% of a treating agent. An aluminum foil which had been subjected toalkali degreasing (2) was dipped in the obtained treating agent, then,aging thereof was carried out at 160° C. for 1 minute to carry out asurface treatment. A thickness of the surface treated film after agingwas 1.3 μm.

Example 1-14

Into deionized water were dissolved PVA resin (A5), TC-400 (B1) andfluorozirconic acid (B2) with a molar ratio of 30:1:25 to obtain 5 wt %of a treating agent. An aluminum foil which had been subjected to alkalidegreasing (2) was dipped in the obtained treating agent, then, agingthereof was carried out at 160° C. for 1 minute to carry out a surfacetreatment. A thickness of the surface treated film after aging was 1.5μm.

Example 1-15

Into deionized water were dissolved PVA resin (A5), TC-400 (B1) andfluorozirconic acid (B2) with a molar ratio of 30:1:75 to obtain 11 wt %of a treating agent. An aluminum foil which had been subjected to alkalidegreasing (2) was dipped in the obtained treating agent, then, agingthereof was carried out at 160° C. for 1 minute to carry out a surfacetreatment. A thickness of the surface treated film after aging was 1.8μm.

Example 1-16

Into deionized water were dissolved PVA resin (A6), TC-400 (B1) andfluorozirconic acid (B2) with a molar ratio of 30:1:25 to obtain 5 wt %of a treating agent. An aluminum foil which had been subjected to alkalidegreasing (2) was dipped in the obtained treating agent, then, agingthereof was carried out at 160° C. for 1 minute to carry out a surfacetreatment. A thickness of the surface treated film after aging was 1.6μm.

Example 1-17

Into deionized water were dissolved PVA resin (A7), TC-400 (B1) andfluorozirconic acid (B2) with a molar ratio of 30:1:25 to obtain 5 wt %of a treating agent. An aluminum foil which had been subjected to alkalidegreasing (2) was dipped in the obtained treating agent, then, agingthereof was carried out at 160° C. for 1 minute to carry out a surfacetreatment. A thickness of the surface treated film after aging was 1.3μm.

Example 1-18

Into deionized water were dissolved PVA resin (A1) and fluorozirconicacid (B2) with a molar ratio of 30:25 to obtain 4.6 wt % of a treatingagent. An aluminum foil which had been subjected to alkali degreasing(2) was dipped in the obtained treating agent, then, aging thereof wascarried out at 100° C. for 30 minutes to carry out a surface treatment.A thickness of the surface treated film after aging was 1.4 μm.

Comparative Example Z-2

Into deionized water were dissolved TC-400 (B1) and fluorozirconic acid(B2) with a molar ratio of 1:25 to obtain 3.8 wt % of a treating agent.An aluminum foil which had been subjected to alkali degreasing (2) wasdipped in the obtained treating agent, then, aging thereof was carriedout at 160° C. for 1 minute to carry out a surface treatment. Athickness of the surface treated film after aging was 0.6 μm.

Preparation conditions of the above-mentioned respective Examples andComparative examples are summarized in Table 3 and Table 4.

TABLE 3 Components of treating agent Aging conditions ConcentrationMetallic Drying of crosslinking Molar ratio temperature solution ExamplePVA resin agent (B) (A:B) (° C.) Time (min) (wt %) 1-1 (A1) TC-400 30:1100 30 2 1-2 (A1) TC-400 30:1 160 30 2 1-3 (A1) TC-400 30:1 200 30 2 1-4(A1) TC-400 10:1 100 30 2 1-5 (A1) TC-400 100:1  100 30 2 1-6 (A1)TC-400 30:1 100 30 5 1-7 (A1) TC-400 30:1 100 30 0.5 1-8 (A1) TC-31030:1 100 30 2 1-9 (A1) Zircosol AC7 30:1 100 30 2 X-1 (A2) TC-400 30:1100 30 2 Y-1 (A3) TC-400 30:1 100 30 2 Z-1 Unmodified TC-400 30:1 100 302 PVA

TABLE 4 Components of treating agent Aging conditions ConcentrationMetallic Metallic Drying of crosslinking crosslinking Molar ratiotemperature solution Example PVA resin agent (B1) agent (B2) (A:B1:B2)(° C.) Time (min) (wt %) 1-10 (A1) TC-400 Fluorozirconic 30:1:25 100 305 acid 1-11 (A1) TC-400 Fluorozirconic 30:1:25 160 1 5 acid 1-12 (A4)TC-400 Fluorozirconic 30:1:25 160 1 5 acid 1-13 (A5) TC-400Fluorozirconic 30:1:13 160 1 5 acid 1-14 (A5) TC-400 Fluorozirconic30:1:25 160 1 5 acid 1-15 (A5) TC-400 Fluorozirconic 30:1:75 160 1 5acid 1-16 (A6) TC-400 Fluorozirconic 30:1:25 160 1 5 acid 1-17 (A7)TC-400 Fluorozirconic 30:1:25 160 1 5 acid 1-18 (A1) — Fluorozirconic30:0:25 100 30 4.6 acid Comparative — TC-400 Fluorozirconic  0:1:25 1601 3.8 example Z-2 acid

(4) Preparation of treating agent of the prior art and surface treatment(treatment using chitosan and chromium fluoride)

As described in the following Comparative examples 1-1 and 1-2, treatingagents of the prior art were prepared and surface treatment of a metalmember was carried out by using these.

Comparative Example 1-1

Into deionized water were dissolved glycerylated chitosan and1,2,3,4-butanetetracarboxylic acid with a weight ratio of 2:1. To theobtained solution was added trivalent chromium fluoride so that theweight ratio thereof to that of the glycerylated chitosan became 2:1 toobtain 2 wt % of a treating agent. An aluminum foil which had beensubjected to alkali degreasing (2) was dipped in the obtained treatingagent, then, aging thereof was carried out at 160° C. for 30 minute tocarry out a surface treatment. A thickness of the surface treated filmafter aging was 2.5 μm.

Comparative Example 1-2

Into deionized water were dissolved glycerylated chitosan and1,2,3,4-butanetetracarboxylic acid with a weight ratio of 1:1 to obtain2 wt % of a treating agent. An aluminum foil which had been subjected toalkali degreasing (2) was dipped in the obtained treating agent, then,aging thereof was carried out at 160° C. for 30 minute to carry out asurface treatment. A thickness of the surface treated film after agingwas 2.4 μm.

Preparation conditions of the above-mentioned respective Comparativeexample 1-1 and 1-2 are summarized in Table 5.

TABLE 5 Components of treating agent Aging conditions ConcentrationMetal Drying of Comparative component temperature solution examplePolymer (A) (B) A:B ratio (° C.) Time (min) (wt %) 1-1 Glycerylated CrF₃4:1 (weight 160 30 2 chitosan + ratio) butanetetra- carboxylic acid 1-2Glycerylated — — 160 30 2 chitosan + butanetetra- carboxylic acid

(5) PP welding 1 (which corresponds to film laminating step to aluminumfoil at the time of preparing aluminum laminate film)

An acid-modified non-stretched PP film was heat sealed (using FCB-200,available from FUJIIMPULSE CO., LTD.), twice, to each aluminum foiltreated by Example 1-1 to 1-9, X-1, Y-1 and Comparative example Z-1 of(3), and Comparative examples 1-1 and 1-2 of (4) at 200° C. for 3 sec toprepare respective test pieces.

(6) Evaluation of corrosion resistance and adhesiveness of test piece ofPP welding 1 after dipping in hydrofluoric acid

Effects of the surface treatment on the aluminum foil were evaluated bydipping the above-mentioned test pieces in 1% hydrofluoric acid underroom temperature for 15 minutes, and whitening (corrosion resistance) ofthe aluminum surface and adhesiveness were measured by the followingmentioned method.

Whitening of aluminum surface: Degree of dissolution of A1 foil wasobserved by naked eyes

Adhesiveness: A1/PP was peeled off by hand, and the stress was confirmed

Evaluation results of corrosion resistance (whitening at the aluminumsurface) and adhesiveness before and after dipping in hydrofluoric acidare shown in Table 6.

TABLE 6 After dipping in hydrofluoric acid Initial stage Whitening at PPadhesiveness PP adhesiveness aluminum surface Example 1-1 ⊚ ⊚ ⊚ Example1-2 ⊚ ◯ ⊚ Example 1-3 ◯ ◯ ⊚ Example 1-4 ◯ ◯ ⊚ Example 1-5 ◯ ◯ ⊚ Example1-6 ◯ ◯ ⊚ Example 1-7 ⊚ ⊚ ⊚ Example 1-8 ◯ ◯ ◯ Example 1-9 ◯ ◯ ◯Comparative Δ~◯ Δ~◯ X example 1-1 Comparative Δ Δ X example 1-2 ExampleX-1 ◯ ◯ ◯ Example Y-1 ◯ ◯ ◯ Comparative Δ Δ Δ example Z-1 * Evaluationstandard of adhesiveness (Good) ⊚ > ◯ > Δ > X (Bad) Evaluation standardof aluminum surface whitening (Good) ⊚ > ◯ > Δ > X (Bad)

(7) PP welding 2

To each aluminum foil which has been treated by Examples 1-1, 1-10 to1-18 and Z-2 of (3) and Comparative example 1-1 of (4) was welded anacid-modified non-stretched PP film on a hot plate at 140° C.×10 sec and165° C.×20 sec, and further welded in an oven at 240° C.×30 sec toprepare respective test pieces.

(8) Evaluation of adhesiveness of PP welding 2 test piece after dippingin electrolyte

The above-mentioned test pieces were dipped in a 1:1 vol/vol % solutionof EC (ethylene carbonate)/DEC (diethylene carbonate) containing 1 mol/Lof LiPF6 at 85° C×7 days, and adhesiveness after dipping in anelectrolyte was measured according to the following method andevaluated.

Adhesiveness: A1/PP was peeled off by hand, and the stress was confirmed

The evaluation results of the adhesiveness before and after dipping inan electrolyte are shown in Table 7.

TABLE 7 After dipping in Initial stage electrolyte PP adhesiveness PPadhesiveness Example 1-1 ⊚ Δ Example 1-10 ⊚ ◯ Example 1-11 ⊚ ◯ Example1-12 ⊚ ◯~⊚ Example 1-13 ⊚ ◯~⊚ Example 1-14 ⊚ ⊚ Example 1-15 ⊚ ◯ Example1-16 ⊚ ◯~⊚ Example 1-17 ⊚ ⊚ Example 1-18 ⊚ Δ~◯ Comparative Δ~◯ Δ example1-1 Comparative ◯ X example Z-2 * Evaluation standard of adhesiveness(Good) ⊚ > ◯ > Δ > X (Bad)

[2. Evaluation of applicability to surface treatment to tab terminalelectrode for Li ion secondary battery]

Li ion secondary batteries were prepared as described in the followingExample 2-1 and Comparative examples 2-1 to 2-2, and applicability ofthe treating agent to the surface treatment of tab electrodes wasevaluated by a leakage test of an electrolyte.

<Preparation of battery for evaluation>

Example 2-1

An aluminum foil was used for the positive electrode current collector,and a copper foil was used for the negative electrode current collector.From these current collectors, to the positive electrode was connected atab terminal of an aluminum foil and to the negative electrode wasconnected a tab terminal of a nickel foil. Also, the surfaces of the tabterminals of the aluminum foil and the nickel foil were subjected tosurface treatment in the same manner as in Example 1-1, and then, amaleated polypropylene film was welded thereto.

The positive electrode was prepared by mixing LiCoO₂ powder as apositive electrode active substance, carbon powder (Ketjen Black) as aconductive agent and PVdF powder as a binder with a weight ratio of90:3:2:5, coating a slurry of the mixture onto the surface of thepositive electrode current collector, and subjecting the resultingmaterial to vacuum heat treatment. An area of the positive electrode was52 cm², and a thickness thereof was 80 pm.

The negative electrode was prepared by mixing graphite powder as anegative electrode active substance and a fluorine resin as a binderwith a weight ratio of 95:5, coating a slurry of the mixture onto thesurface of the negative electrode current collector, and subjecting theresulting material to vacuum heat treatment. An area of the negativeelectrode plate was 58 cm², and a thickness thereof was 65 μm.

As a separator, a porous film comprising a polypropylene was used. Theabove-mentioned positive electrode, the separator and the negativeelectrode were laminated to prepare an electrode unit.

As a non-aqueous electrolyte, a material in which 1 mol/L of LiPF₆ hadbeen dissolved in a mixed solvent of ethylene carbonate (EC) and diethylcarbonate (DEC) with a volume ratio of 5:5 was used.

Then, an aluminum laminate film was folded so that the above-mentionedelectrode unit was sandwiched, three sides (upper edge portion and bothside edge portions) were heat sealed to form an exterior body, and 3 mlof the above-mentioned non-aqueous electrolyte was injected therein.Incidentally, when the upper edge portion was to be sealed, sealing wasso carried out that the tab terminals were sandwiched.

Comparative Example 2-1

A Li ion secondary battery was prepared in the same manner as in Example2-1 except for carrying out the same surface treatment as in Comparativeexample 1-1 to the surface of the tab terminals of the positive andnegative electrodes.

Comparative Example 2-2

A Li ion secondary battery was prepared in the same manner as in Example2-1 except for carrying out the same surface treatment as in Comparativeexample 1-2 to the surface of the tab terminals of the positive andnegative electrodes.

<Leakage test>

Each 10 batteries of the above-mentioned Example 2-1, and Comparativeexamples 2-1 to 2-2 were subjected to a discharge test in athermohygrostat bath at a temperature of 40° C. and a humidity of 90% byapplying a load of 3.8V. As a result, with regard to the batteries ofExample 2-1 and Comparative example 2-1, no abnormality was admitted inall 10 samples of the batteries after 7 days. On the other hand, withregard to the batteries of Comparative example 2-2, leakage of anelectrolyte from the tab terminal portion was admitted in all 10batteries among 10 samples.

From the results, it could be confirmed that the treating agent of thepresent invention could be applied to the surface treatment of a tabterminal electrode for a Li ion secondary battery.

[3. Evaluation of applicability of aluminum laminate package for Li ionsecondary battery to aluminum substrate surface treatment]

Li ion secondary battery was each prepared as described in Example 3-1and Comparative examples 3-1 to 3-2, and an applicability of thetreating agent to the surface treatment of an aluminum substrate of analuminum laminate package was evaluated by a leakage test of anelectrolyte.

<Preparation of battery for evaluation>

Example 3-1

The surface treatment was carried out in the same manner as in Example1-1 except for coating the treating agent to an aluminum foil uniformlyas an aluminum laminate package. Thereafter, a Nylon film wasdry-laminated on one surface of the surface treated aluminum foil byusing a urethane 2-liquids adhesive, and a maleic anhydride-modifiedpolypropylene film was heat-laminated on the other surface to obtain analuminum laminated film.

An aluminum foil was used for the positive electrode current collector,and a copper foil was used for the negative electrode current collector.From these current collectors, to the positive electrode was connected atab terminal of an aluminum foil and to the negative electrode wasconnected a tab terminal of a nickel foil. Also, the surfaces of the tabterminals of the aluminum foil and the nickel foil were subjected tosurface treatment in the same manner as in Example 1-1, and then, amaleated polypropylene film was welded thereto.

The positive electrode was prepared by mixing LiCoO₂ powder as apositive electrode active substance, carbon powder (Ketjen Black) as aconductive agent, and

PVdF powder as a binder with a weight ratio of 90:3:2:5, coating aslurry of the mixture onto the surface of the positive electrode currentcollector, and subjecting the resulting material to vacuum heattreatment. An area of the positive electrode was 52 cm², and a thicknessthereof was 80 μm.

The negative electrode was prepared by mixing graphite powder as anegative electrode active substance and a fluorine resin as a binderwith a weight ratio of 95:5, coating a slurry of the mixture onto thesurface of the negative electrode current collector, and subjecting theresulting material to vacuum heat treatment. An area of the negativeelectrode plate was 58 cm², and a thickness thereof was 65 μm.

As a separator, a porous film comprising a polypropylene was used.

The above-mentioned positive electrode, the separator and the negativeelectrode were laminated to prepare an electrode unit.

As a non-aqueous electrolyte, a material in which 1 mol/L of LiPF₆ hadbeen dissolved in a mixed solvent of ethylene carbonate (EC) and diethylcarbonate (DEC) with a volume ratio of 5:5 was used.

Then, the above-mentioned aluminum laminate film was folded so that thepolypropylene film became inside and the above-mentioned electrode unitwas sandwiched, three sides thereof (upper edge portion and both sideedge portions) were heat sealed to form an exterior body, and 3 ml ofthe above-mentioned non-aqueous electrolyte was injected therein.Incidentally, when the upper edge portion was to be sealed, sealing wasso carried out that the tab terminals were sandwiched.

Comparative Example 3-1

A Li ion secondary battery was prepared in the same manner as in Example3-1 except for using the same treating agent as in Comparative example1-1 to the surface treatment of the aluminum foil of the aluminumlaminated film.

Comparative Example 3-2

A Li ion secondary battery was prepared in the same manner as in Example3-1 except for using the same treating agent as in Comparative example1-2 to the surface treatment of the aluminum foil of the aluminumlaminated film.

<Leakage test>

Each 10 batteries of the above-mentioned Example 3-1, and Comparativeexamples 3-1 to 3-2 were subjected to a discharge test in athermohygrostat bath at a temperature of 40° C. and a humidity of 90% byapplying a load of 3.8V. As a result, with regard to the batteries ofExample 3-1 and Comparative example 3-1, no abnormality was admitted inall 10 samples of the batteries after 7 days. On the other hand, withregard to the batteries of Comparative example 3-2, leakage of anelectrolyte from the aluminum laminate periphery portion was admitted inall 10 batteries among 10 samples.

From the results, it could be confirmed that the treating agent of thepresent invention could be applied to the surface treatment of analuminum substrate of an aluminum laminate package for a Li ionsecondary battery.

UTILIZABILITY IN INDUSTRY

The metal surface treatment agent for a lithium secondary battery of thepresent invention can improve interlaminar adhesiveness between themetal material and the resin coating layer such as a film or a coatedfilm and solvent resistance without using chromium, so that it can beutilized for a package for a lithium ion secondary battery, orfilm-attached tab lead member.

1. An aqueous metal surface treatment agent for a lithium ion secondarybattery which comprises a polyvinyl alcohol resin containing 2 to 15 mol% of a 1,2-diol structural unit represented by the formula (1):

wherein R1, R2 and R3 each independently represent a hydrogen atom or anorganic group, X represents a single bond or a connecting chain, and R4,R5 and R6 each independently represent a hydrogen atom or an organicgroup, and having a degree of saponification of 90 to 99.9 mol % and anaverage degree of polymerization of 250 to 3000; and a metalliccrosslinking agent.
 2. The metal surface treatment agent according toclaim 1, wherein a molar ratio of the polyvinyl alcohol resin:themetallic crosslinking agent is 1:5 to 500:1.
 3. The metal surfacetreatment agent according to claim 1, wherein the metallic crosslinkingagent is selected from the group consisting of an oxide, a hydroxide, acomplex compound, an organometallic compound, an organic acid salt andan inorganic acid salt of titanium, aluminum, zirconium, vanadium,molybdenum, cerium, lanthanum or tungsten.
 4. The metal surfacetreatment agent according to claim 2, wherein the metallic crosslinkingagent is selected from the group consisting of an oxide, a hydroxide, acomplex compound, an organometallic compound, an organic acid salt andan inorganic acid salt of titanium, aluminum, zirconium, vanadium,molybdenum, cerium, lanthanum or tungsten.